// 应有全局样式
body,
html {
  height: 100%;
  width: 100%;
}

div,
p,
ul,
li {
  padding: 0;
  margin: 0;
  list-style: none;
}

.PA {
  position: absolute;
}

.PR {
  position: relative;
}

a {
  text-decoration: none;
}